1. Field of the Invention
The present invention relates to an image forming apparatus wherein a toner image formed on a photoconductive body is first transferred onto an intermediate transferring body (primary transfer) and, then, the transferred toner image is transferred onto a copy paper (secondary transfer) to obtain a hard copy.
2. DESCRIPTION OF THE PRIOR ART
Recently, such a copy machine as mentioned above (hereinafter referred to as a copy machine of secondary transfer type) is on the market. This type of copying machine is used for a full color copying machine as an example. In the full color copying machine of secondary transfer type, for instance, an electrostatic latent image formed on the photoconductive body by passing a reflected light through a blue color filter is developed with yellow toner and the developed image is transferred onto an intermediate transferring body at first. Next, an electrostatic latent image formed using a green color filter is developed with magenta toner and the developed image is transferred onto the intermediate transferring body to superimpose the same on the image developed with yellow toner and, thereafter, an electrostatic latent image formed using a red color filter is developed with cyan toner and the developed cyan toner image is superimposed on the yellow and magenta toner images by transferring the same onto the transferring body. The full color image thus formed by superimposing three toner images on the transferring body is transferred on a copy paper secondarily to give a full color copy.
Usually, an endless belt of a flexible dielectric film such as polyimido film is used for the intermediate transferring body.
In the image forming apparatus such as the full color copying machine, troubles such as paper jams are often caused on the way of conveying copy papers.
Conventionally, when such a trouble is caused, copy actions having been performed until then are automatically canceled and a series of copy actions including a document scan--formation of a latent image on a photoconductive body--a development with toner--transfer of the image onto an intermediate transferring body--copy paper feeding--transfer of toner image onto a copy paper--fixing and discharge of the copy paper has to be repeated from the beginning after removing the copy paper which had been jammed.
However, assuming such a case that a paper jam is caused on the way of the path for transporting copy papers to the secondary transferring station, the secondary toner PG,4 image to be transferred onto a copy paper is maintained on the intermediate transferring body without any damage due to the paper jam since it is caused before reaching the secondary transferring station. In other words, the secondary toner image is kept in a transferable state nevertheless.
Accordingly, it is wasteful with respect to toner, time, electric power and the like to repeat the series of copy actions from the beginning in such a case as mentioned above.